In chloroform solution, the syn/anti rotamer ratios for AT-(2-pyridyl)carbamates, 3, and JV-phenylcarbamates, 4, are close to 0.05. Addition of the double hydrogen bonding acetic acid moderately stabilizes the syn rotamer of 4, but has no measurable effect on the syn/anti ratio for 3. Conversely, the hydrogen bond donor-acceptor-donor triad in 2,6-bis(octylamido)pyridine, 1, strongly stabilizes the syn rotamer of 3, but has no effect on the syn/anti ratio for 4. The K& for syn-3:l is 103-104 times higher than the K1 for anti-3:l. This implies that the alkoxy oxygen in anti-3 is a much poorer hydrogen bond acceptor than the carbonyl oxygen in syn-3, most likely because of a combination of steric and electrostatic factors.
ASJC Scopus subject areas
- Organic Chemistry